A novel digitally-controlled varactor for portable delay cell design

Pao Lung Chen*, Ching Che Chung, Chen-Yi Lee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In this paper, a novel digitally-controlled varactor (DCV) for portable delay cell design is presented. The proposed varactor uses the gate capacitance differences of NAND/NOR gates under different digital control inputs to build up a digitally-controlled varactor. Then the proposed varactor is applied to design a high resolution delay cell and to achieve a fine delay resolution. Different types of NAND/NOR gates (2-input or 3-input) for DCV design are also investigated in this paper. The proposed DCV can be implemented with standard cells, thus it can be easily ported to different processes in a short time. A test chip fabricated on a standard 0.35 μm CMOS 2P4M process proves that the proposed delay cell has a fine delay resolution about 1.55 ps. As a result, the proposed DCV exhibits finer resolution, better linearity, and better portability than traditional delay elements, and is very suitable for portable delay cell design.

Original languageEnglish
Pages (from-to)3324-3326
Number of pages3
JournalIEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Issue number12
StatePublished - 1 Jan 2004


  • Cell-based
  • DCO
  • Digitally-controlled varactor (DCV)
  • DLL
  • Portable delay element

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